Directional and trim control for rotary wing aircraft



April 24, 1951 G. s, DOMAN 2,550,538

DIRECTIONAL AND TRIM CONTROL FOR ROTARY WING AIRCRAFT Filed Aug. 9, 1946if' J i Y# 4 Y i3' @yf INVENTOR. L" g @L/DDE/v 500m/v Tro/QN'EYSPatented Apr. 24, 1951 DIRECTIONAL AND TRIM CONTROL FOR ROTARY WINGAIRCRAFT Glidden S. Doman, Stratford, Conn., assignor to DomanHelicopters, Inc., a corporation of Dela- Ware Application August 9,1946, Serial No. 689,458

22 Claims.

The invention relates to a directional and trim control for rotary wingaircraft having wings or blades mounted for change of their pitch. Theconstruction in its more detailed form also includes a gyroscopicstabilizing means to automatically maintain the azimuth plate in xedtrim position in space as determined by a gyroscope throughout shortterm variations in the attitude of the fuselage but which changes theazimuth plate trim position according to long term change of fuselageattitude.

It is an object of the invention to construct a new and novel trim anddirectional control for rotarywing aircraft.

Another object is to constructza trim and directional control whichexerts a centering force so that the pilot can feel in the stick, theextent of directional pitch change of the wings or blades.

A stillfurther object is to providea new and novel gyroscopic control ofthe azimuth plate trim of a rotary wing aircraft Another object is toconstruct a` trim and directional control in which the directionalcontrol is superimposed upon a trim control and gyroscopic meansautomatically maintains the trim control throughout minor fuselagemotions.

Other objects of the invention will be more apparent from the followingdescription when taken in connection with the accompanying drawingsillustrating a preferred embodiment of the invention in which:

Figure l is a diagrammatic View ofthe control for a rotary wingaircraft.

Figure 2 is an enlarged partial view of gyro scopically controlledswitches for the trim control.

Figurer3 is a section through the gyroscope.

Figure 4 is a View showing a simplified confstruction without gyroscopiccontrol.

In the piloting of previous rotary wing aircraft such as helicopterswhich utilize cvclic pitch change of the wings or blades in order tocontrol direction and speed of ilight, the pilot is required toconstantly overcome varying trim forces which are exerted against thestick. In addition the trim position of the stick will vary during anyaccelerations of the craft and for every change in the center of gravityof the loaded aircraft. It is desirable that a central or a neutralposition beY maintained for the stick irrespective of the trim l oracceleration conditions of the aircraft to `aid the pilot in intentionalmaneuvering. The invention herein corrects for these difcultiesencountered by a pilot and in addition thereto provides a simplemechanism for accomplishing these results.

(Cl. 24d-17.13)

In a rotary wing aircraft, the rotor head is mounted upon the aircraftin any suitable fashion and usually it is mounted upon a hollow mast Iwhich is secured to the fuselage. A drive shaft Il may extend throughthe hollow mast l0 and rotate the rotor head. The rotor head includes aplurality of wings or blades l2,` one of which is shown, each mountedupon a shaft I3 coextensive with the longitudinal axis of the wing forpitch change of the latter. The shaft may be connected by an arm i4 toone end of a connecting link I5. 'Ihe other end of the link isvconnected with an azimuth plate I6 which is mounted upon thel mast inknown manner for universal inclination in any direction.

Inclination of the azimuth plate provides for cyclic change of pitch ofthe wings of the rotor head as the head is rotated. Collective change ofthe pitch of the rotary wings ofthe aircraft is usually provided also,and for this purpose a sleeve I1 may be slidably mounted upon the mastI0 and moved vertically thereon by means of suitableoperating mechanism,not shown, but connected with the link I8. With a rotor head which isconstructed for collective pitch control, the trim and directionalcontrol to be described herein is mounted together with the azimuthplate I6 upon the sleeve il.

The trim and directional controlcomprises a pair of operating means eachbeing located or spaced with respect to each other from the axis of themast. This pair of operating means is therefore able to incline theazimuth plate in any direction for cyclic pitch control of the wings orblades of the rotor head. Since each operating means is a duplicate ofthe other, one only will be described in detail.

The operating means includes a trim control member 22 which is movedupwardly and downwardly with respect to the sleeve i1 and the air craft.The trim control member, in its more detailed form as illustrated,embodies three distinct control means, particularly shown as threehydraulic cylinders, the construction and operation of which will appearhereinafter. The three control means are a manually operable directioncontrol, a manually operable trim adjustment and a gyroscopicallyoperated means for maintaining trim.

The trim adjustment preierablyis an hydraulic cylinder '5 forming a partof. the trim control member A22 in which there is aluid piston 23. Thepiston is connected by a piston rod 24 to the sleeve l1 or Va suitable.extension4 thereof. When gyroscopic control is provided as well, the

piston rod 2li is connected with the sleeve Il through a gyroscopiccage, ring or sphere 2G which is carried by the sleeve il, and anadditional actuating cylinder 5I which responds to a changed position ofthe cage as will appear more fully hereinafter. Upon the introduction offluid pressure into either end of the cylinder 25, the piston 23 movesupwardly or downwardly within the cylinder and changes the inclinationof the cage 25 relative to the azimuth plate and in turn directs fluidinto the cylinder 5i which raises or lowers the control means 22,tilting the azimuth plate relatively to the mast. A simple form is shownin Figure 4 without gyroscopic control and in which the piston isdirectly connected with the sleeve li as will'be described hereinafter.

A directional control member 2l operates from the trim control membe1,22. This member preferably is an hydraulic piston 2l operating in acylinder 23 forming a part of the trim control member 22. rlhe piston 27is connected through its piston rod 25 and a link 3U with the azimuthplate i6. Spring means are provided to centralize the directionalcontrol member or piston 21 withrespect to the trim control member. Thisspring means may be of any suitable form, that illustrated including aspring 5l between the piston 2l and one end of the cylinder 28 and asecond spring 32 extending between the piston 2l" and the other end ofthe cylinder 28. IThis spring means centralizes the piston 21 withrespect to the cylinder or the trim control member 22.

= Manually operable means are provided for both the trim control and thedirectional control.

vWith hydraulic or uid operating means, the manually operable trimcontrol means includes a fluid cylinder 35 which is Xed to the aircraft.This cylinder contains a piston 36 connected by a piston rod 3l to atrim control handle 38. One end offthe cylinder 35 is connected by apipe 39 to one end of the cylinder 25 and the other end of the cylinderby a pipe lll) to the other end of the cylinder 25. Irreversible valves4| are provided preferably close to cylinder 25 in each pipe for safetyin the event that there is a liuid line failure. Moving of the controlhandle forces fluid from the cylinder 35 Yinto the cylinder 25 andmoves'the piston 23 therein which in turn adjusts the position of thecage 25, or moves the control means 22 directly if gyroscopic control isnot provided.

Manually operable direction control means is provided which ispreferably hydraulic and includes a cylinder 43 having a piston 44 whichis connected by a piston rod 45 to a directional control handle llS. Oneend of the cylinder d3 is connected by a pipe il to one end of thecylinder 28 and the other end of the cylinder is connected by a pipe d8to the other end of the cylinder 28. Movement of the handle forces iiuidfrom cylinder 53 into cylinder 2e and moves the directional controlmember or piston 2l against the compression of the spring means andchanges the inclination'of the azimuth plate.

The directional and trim control will preferably include a gyroscopicstabiizing control for automatically maintaining the trim inclination ofthe azimuth plate fixed in space regardless of short te# i variations inattitude of the fuselage or aircraft. The gyroscopic control preferablyis a iiuid system including a cylinder 5l forming a part of the trimcontrol member 22 and having a uid piston 52 therein carried by a pistonrod 53 which secured to the sleeve l? or a suitable 4 extension thereof.Each end of the cylinder 5l is connected by pipes 54 and 55 to valves 56and 5'! respectively which may be electrically operated. The valves areconnected by pipes 58 and 59 to a iluid pump 50.

The electrically operated valves are opened or closed by gyroscopicmeans which includes a gyroscopic member S3 which is independentlyrotated by any desirable means such as a motor 64. A gyroscopic meansmay be provided for each operating means; however, it is simpler to usea single gyroscopic means to serve both operating means. For singlegyroscopic means, the gyroscopic member controls two pairs of switcheswhich are carried by the universally mounted cago ring or sphere 25. Onepair of switches controls the operation oi one pair of valves 5B and 5'!and the other pair of switches controls the operation of valves 56 and5l. The switches may include a contact resiliently carried by or movablewith the gyroscopic member and contacts 55 and 5l on each side thereof,each being connected by wires 63 and 65 to its respective valve 56 and51. At right angle to the contacts '66 and 67 are like switch contacts55 and 5? which are connected with their counterpart valves 5G' and 5?'.These switch contacts are placed close to the gyroscopic contact 65 sothat any change in the attitude of the aircraft closes one or two of theswitch contacts which are adjacent to each other.

The gyroscopic member is damped by suitable friction or dash pot dampers'I5 at right angles to each other. The dampers are adjusted for softoperation, that is the gyroscope is insensitive or substantiallyinsensitive to short term changes in attitude of the aircraft but thedampers are stiff enough to cause the gyroscopic meinber to gradualyassume a new plane of rotation or reference plane perpendicular to themast I0 upon long term change of attitude of the craft and the azimuthplate will be adjusted to a new trim position comparable to such changein the plane of rotation of the gyroscopic member.

if a short term change in attitude of the aircraft should occur such asby gustiness and theY like, the gyroscopic member 53 maintains itsposition untilted in space so that one or more switch contacts areclosed. This opens the valve or valves connected with the switch contactor contacts and forces fluid into one end of the cylinder 5l or itscounterpart cylinder 5l to adjust thc position of its respective trimcontrol member 22 and thereby maintains the azimuth plate IG in itsposition relative to the gyroscopic member or in Xed position in space.Upon adjustment of the trim position of the azimuth plate, the cage andswitch contacts again assumes a neutral position with respect to thegyrosccpic member whereupon the respective uid valve or valves close andthe rotor remains in adjusted trim position.

The operation of the complete control will be described. In order toobtain trim of the aircraft, the handle 38 or its counterpart 38 is orboth handles are operated which forces iiuid from the cylinder 35 intothe cylinder 25 or its counterpart cylinder 25' or both cylinders which.moves the piston 23 and hence the gyroscope 25, since the trim controlmember 22 is held stationary by the duid in the cylinder 5l. This cagemotion closes a switch such as 5l and admits iiuid to cylinder 5l,tilting the azimutlfi plate through the springs 3l and 32 while cage 25is also returned to normal position with vspect tov the gyroscope 53.YWhen desired trim locked in adjusted position and the trim controlmember 22 remainsV in trim adjusted position. Thereafter the gyroscopicmeans operates to maintain trimA of the aircraft as described above. Itisv to be understood that the handles 38 and 38 may be a single leveruniversally mounted in known fashion to operate either or both pistons36 or 36 as desired.

For directional control, the pilot operates the handle (i6 or itscounterpart dfi' or both handles which. introduces fluid from thecylinder i3 into its respective cylinder 28 or 28' which moves thepiston. 2l. in its cylinder 28 against the compressionof the springmeans. The azimuth plate l is inclined by the movement of the piston 2lto cyclically varythe pitch of the Wings which inclination is inaddition to the inclination initially provided by the trim controlmeans. It will be observed that the pilot, in maneuvering the aircraft,operates against the spring means so that the amount of directionalcontrol or inclination applied to the azimuth plate will be felt in thestick when maneuvering or fiying. It is to be understood also that thehandles E and 46 may be a single handle universally mounted to operatethe piston 44 and d' or both as desired. The craft may also be flown andmaneu- Vered with the trim control devices with no recourse to theregular directional control. This factprovides a safety factor againstany fluid line l.

failure.

Figure 4 shows a simplified construction without gyroscopic control, itscylinder and associated mechanism. The manual trim control cylinder isshown connected with the cylinder 5I for direct adjustment of the trimcontrol member 22. In other words when gyroscopic control is notprovided, the manual control cylinder 3e may be directly connected withthe cylinder 5l or this may be expressed also as the cylinder 25 ofFigure 1 may be substituted for the cylinder 5I.

This invention is presented to fill a need for improvements in adirectional and trim control.

It is understood that various modifications in structure, as well aschanges in mode of operation, assembly, and manner of use, may and oftendo occur to those skilled in the art, especially 4after benefiting .fromthe teachings of an invention. Hence, it will be understood that thisdisclosure is illustrative of preferred means of embodying the inventionin useful form by explaining the construction, operation and advantagesthereof.

What is claimed is:

l. A trim and directional control for rotary wing aircraft having auniversally inclinable azimuthplate device for pitch control of thewings comprising operating. means adapted to be connected between afixed part of the aircraft and the azimuth plate, the operating meansincluding a movable trim controlmember, a directional control memberadapted to be connected with the azimuth plate, spring means engagingthe movable trim control member and the directional control .member tomove the latterthrough the spring means upon movement of the formermember, a control means connected with the aircraft'and the movablemember to change the position of the latter, the spring means and thedirectional control member, and manually operable directional controlmeans connected with the directional control member to move the latteragainst the resistance of the spring means..

2. A trim and directional control for rotary wing aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomprising operating means adapted to be connected between a fixed partof the aircraft and the azimuth plate, the operating means including. amovable trim control member, a directional control member adapted to beconnected with the azimuth plate, spring means engaging the movable timcontrol member and the directional control member to move the latterthrough the spring means upon movement of the former member, manuallyoperable trim control means connected with the aircraft and the movablemember to change the position of the latter, the spring means and thedirectional control member, and manually operable directional controlmeans connected with the directional control member to move the latteragainst the` resistance of the spring means.

3. A. trim and directional control for rotary wing aircraft having auniversally inclinable azimuth plate for` pitch control of the wingscomprising operating means adapted to be connected between a fixed partof the aircraft and the azimuth plate, the operating means including amovable trim control member, a directional control member adapted to beconnected with the azimuth plate, spring means engaging the. movabletrim control member and the directional control member to move thelatter through the spring means upon movement of the former member, trimcontrol means connected with the aircraft and the movable member tochange the position of the latter, the spring means and the directionalcontrol member including gyroscopic means to automatically adjust theposition of the movable member and hence the azimuth plate relatively tothe aircraft upon short term change in attitude of the aircraft andholding the azimuth plate in position in space, and manually operabledirectional control means connected with the directional control memberto move the latter against the resistance of the spring means.

d. A trim and directional control for rotary Wing aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomprising operating means adapted to be connected between a fixed partof the aircraft and the azimuth plate, the operating means including amovable trim control member, a directional control member adapted to beconnected with the azimuth plate, spring means engaging the movable trimcontrol member and the directional control member to move the latterthrough the spring means upon movement of the former member, manuallyoperable trim control means connected with the aircraft and the movablemember to change the position of the latter, the spring means and thedirectional control member, gyroscopic means connected with the movablemember to automatically adjust the position of the movable member andhence the azlmuth plate with respect to the aircraft upon short termchange in attitude of the latter and holding the azimuth plate inposition in space, and manually operable directional control meansconnected with the directional control member to move the latter'against the resistance of the spring means;

5. A trim and directional control for rotary wing aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomprising a pair of operating means adapted to be connected bewteen afixed part of the aircraft and the azimuth plate and located 90 apartwith respect to each other, each operating means including a movabletrim control member, a directional control member adapted to beconnected with the azimuth plate, manually operable trim control meansconnected with the aircraft and the movable member to change theposition of the latter, gyroscopic means connected with both movablemembers to automatically adjust the position of both movable members andhence of the azimuth plate with respect to the aircraft upon short termchange in attitude thereof and holding the Y azimuth plate in positionin space and manually operable directional control means connected withthe directional control member to move the `latter against theresistance of the spring means.

6. A trim and `directional control for rotary wing aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomprising a pair of operating means adapted to be connected between aXed part of the aircraft and the azimuth plate and located 90o apartwith respect to each other, each operating means including a movabletrim control member, a directional control member adapted to beconnected with the azimuth plate, spring means engaging the movable trimcontrol member and the directional control member to move the latterthrough the spring means upon movement of the former member, manuallyoperable trim control means connected with the aircraft and the movablemember to change the position of the latter, the spring means and thedirectional control member, gyroscopic means connected with both movablemembers to automatically ad- `iust the position thereof and hence theazimuth plate with respect to the aircraft upon short term change inattitude thereof and holding the azimuth plate in position in space, andmanually operable directional control means connected with thedirectional control member to move the latter against the resistance ofthe spring means.v

'7. A trim and directional control for rotary wing, aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomp-rising a pair of operating means adapted to be connected between afixed part of the aircraft and the azimuth plate and located 90 apartwith respect to each other, each operating means including a movabletrim control member, a directional control member adapted to beconnected with the azimuth plate, manually oper* able trim control meansconnected with the aircraft and the movable trim control member tochange the position of the latter and the directional control member;gyroscopic means connected with both movable members to automaticallychange the position thereof and hence of the azimuth plate with respectto the aircraft upon short term change in attitude of the latter andholding the azimuth plate in position in space including a gyroscopicmember, means to rotate the gyroscopic member, two pairs of switch meanscontrolled by the gyroscopic member at least one of which is closed uponinclination of the aircraft, hydraulic valve means operated by eachswitch means, and hydraulic means connected with each pair of valves andthe movable trim control member to adjust the latter upon inclination ofthe aircraft; and manually operable directional control means connectedwith the directional control member to move the latter.

8. A. trim and directional control for rotary wing aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomprising a pair of operating means adapted to be connected between afixed part of the aircraft and the azimuth plate and located apart withrespect to each other, each operating means including a movable trimcontrol member, a directional control member adapted to be connectedwith the azimuth plate, spring means engaging the movable trim controlmember and the directional control member to move the latter through thespring means upon movement of the former member, manually operable trimcontrol means connected with the aircraft and the movable member tochange the position of the latter, the spring means and the directionalcon- .rol member; gyroscopic means connected with both movable memberstc automatically change the position of both movable members and henceof the azimuth plate with respect to the aircraft upon short term changein attitude of the latter and holding the azimuth plate in position inspace including a gyroscopic member, means to rotate the gyroscopicmember, two pairs of switch means controlled by the gyroscopic member atleast one of which is closed upon inclination of the aircraft, hydraulicvalve means operated by each switch means, and hydraulic means connectedwith each pair of valves and the movable trim control member to adjustthe latter upon inclination of the aircraft; and manually operabledirectional control means connected with the directional control memberto move the latter against the resistance of the spring means.

9.A trim and directional control for rotary wing aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomprising a pair of operating means adapted to be connected between afixed part of the aircraft and the azimuth plate and located 90 apartwith respect to each other, each operating means including a movabletrim control member, a directional control member adapted to beconnected with the azimuth plate, at least one of said members being anhydraulically operated member, spring means engaging the movable trimcontrol member and the directional control member to move the latterthrough the spring means upon movement of the former member, manuallyoperable trim control means connected with the aircraft and the movablemember to change the position of the latter, the spring means and thedirectional control member, gyroscopic means connected with both movablemembers to automatically adjust the position of both movable members andhence of the azimuth plate with respect to the aircraft upon short termchange in attitude of the latter and holding the azimuth plate inposition in space, manually operable directional control means connectedwith the directional control member to move the latter against theresistance of the spring means, and at least one of the manuallyoperable control means being hydraulically operated.

l0. A trim and directional control of rotary Wing aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomprisiriaa pair of operating' meansi adapted to be connectedlbetween'afixed part 'of the' aircraft and thetazimuthr. plate and located 498,Uapartiwith respectto. eachi other, each. operating meansfi'n- 'cludingva movable trim: controlmember,v a `di,-

r'efctionalA control member adapted to be connected. with the azimuthplate, atleast one of I said?- members beingfv anv hydraulically'operatedmemb'er, springA means. engaging-the movablev trim? control in)tr-.ber` and the directional control n-iembertoinlovey the latterthrough the spring means-uponmovementoftheformer member,

manually'operable trim control means connectedA i acopiomember,` ltwo'pairs Vof switchr'n'eanscon`- trolled by' the gyroscopic'member atleast 'one` of whi'chis closedl'upon' inclination ofthe' aircraft,hydraulic valvev means voperated byeach'switch means, and hydraulic'means connected with eaciipair of valves and thejmovable trim controlmember to' adjust the'- latter upon inclinationof theaircraityandmanually operable directional controll meansconnectedwith thedirectional control memberV to move the" latter against the resistanceof the springl means, and at least one anddirectional control for rotaryn lilydrauli'callyoperated. f`

aain'iutli'plate orp'itchco-ntrol of the' wings compricing pairof`operating means adapted: tobe connected betweenya xcdpart' oftheaircrafty n a azimuth platfe and located 90` apart with t' tojgeach`other each operating means. in-l n'iovable trim control member, a difnected` with the "azimuth, rplate Y and 'connected with the vinova-ble''trim control member to move' theimernber" with the latter, andVmanually' Operabletdirectibnal control meansconnected withv tlielIdirectional control member'to move the same independently, and"`alutomaticallyl operable trim coiitrojlrmeans connected with the"aircraft" and` themovablecmembers to changethe positionsof` the `vlatterand' theirdirecti'onal 'control'member` including vcage means mountedfor inclination with Yrespect to; thefaircraft, gyroscopic `meansmounted upon the aircraft for universal inclination withrespect theretoand located within the cage' means, meansto drivethe gyroscopic means,.dampers Vcoi`1ne-cted with the gyroscopic means' which are sufficiently`softto render thegyroscopic meansrinsensitive* toLshort term changesof, attitild'el` ofthe' aircraft and yet'change its inclinat'iotofollow"longtermichanges in attitude; four' switch means` carried bythecage means and' at least* one of which is operated by the gyroscopicmeans upon inclination of theaircraft` in any A direction,` and'apairoftrim'control means for: i eachmovable trim control member andfeach con`trolled `by switch lmeans" 'upon' inclination of the` aircraft. Y

125 Av tri-manddirectional control for rotary wingjfaircra'ft" having aluniversally inclinable uth plate for pitchfcontrol of the wingscomprising? arfp'airo'f operating' means 'adapted to* be-` of themanually"operablel control means bei-ng 'Y chal controlrnember' adaptedto be conwing* air rait' having" a# 4u niversally 4 inclinable loconnected. between a'nxed part of the aircraft andi theazimuth plate andlocated 99 apart-with respect to`- each other, cach operating meansincluding a movableA trim. control member, a direction'al control memberadapted to be connected with the azimuth plate and connected. withthemovable trim control member to move with the latter, `manually operateddirectional control means connected: with the directional control memberto move the same independently; automatieallly operable trim controlmeans connected with they aircraft and the movable members to changethepositionsofthe latter, their spring means and their directional controlmember in'- clu'ding cage means mounted for inclination with respecttothe aircraft, gyrosco'pic means mountedl upon the aircraftfor'universal inclination with respect thereto and' located within thecage a means'to drive the-gyroscopic means, dampersl connected withV thegyroscopic means such. that the gyroscopic'means is insensitive to" ashort term' change of attitude of the attitude ofthe aircraft butchanges its inclination upon longterm change in attitude, four switchmeans carried by the cage means and at least one of which closed` by thegyroscopic means upon inclination of the aircraft in' any direction, anda pair' of'trimV control means for each movable tri'm controll memberand each controlled by a switch means to adjust the position of at leastonetrim control` member upon inclination of the aircraft; andiA manuallyoperable, trim control means to independently change the 'position ofthe cage means;

13. A trim and directional control for rota-ry Wing aircraft 4having auniversally inclinable azimuth plate for pitch control of the Wingscomprising a pair of operating means adapted to be connected' between axedvpart of the aircraft and? the azimuth plate and located apart withrespect to each other, each operating means including a movable trimcontrol member,` a directional control member adapted to be connectedwith the azimuth plate, spring means engage ing the' movable tri-mcontrol member and .the directional control member to move the latterthrough` the spr-ing means upon movement offthe former member, manuallyoperatedl Vdirectional control?"meanslconneoted with the directionalvcontrol member to move the same independently; automatically operable'trim control means con'- riected with the' aircraft and the movablevmembers to change the positions of? the latter, their springmeans and theirdirectional control member* including cage means mounted for inclinationwithr respectV tothe aircraft, gyroscopicV means` mounted upon theaircraft for universal inclinationwithrespect thereto and locatedwithi-nthe cage means, means to drive the gyroscopc means, dampers connectedwith the gyrosco'pic means which render the latter insensitive to" ashort termi change' ofv attitude of the aircraftbutl change litsinclination upon long term change'lin` attitude, four-'switch meanscarried by the-cagex means'and atV least one of which is operated-by thegyroscopic meansupon inclinationof tho-airLe craft-"in any direction,anda pair of trim control means A` for each movable trimc'ontrol member'ardeachcontrolled by aswitch means to adjust the position ofat least onetrim control member@ upon inclination of the aircraft.

14. A trim and directional control for rotary Wing 'aircraft' having a-vuniversallyinclinable" azimuth plate for pitch control of thewingsco'mpris'ingfa pair of operating means adapted to be i l connectedbetween a fixed part of the aircraft and the azimuth plate and located90 apart with respect to each other, each operating means including amovable trim control member, a directional control member adapted to beconnected with the azimuth plate, spring means engaging the movable trimcontrol member and the directional control member to move the latterthrough the spring means upon movement of the former member, manuallyoperated directional control means connected with the directionalcontrol member to move the same independently; automatically operabletrimcontrol means connected with the aircraft and the movable members tochange the positions of the latter, their spring means and theirdirectional control members including cage means mounted for inclinationwith respect to the aircraft, gyroscopic means mounted upon the aircraftfor universal inclination with respect thereto and locatedwithin thecage means, dampers connected with the gyroscopic means which rendersthe-latter insensitive to a short term change of attitude of theaircraft but change its inclination upon long term change in attitude,four switch means carried by the cage meansY and at least one of whichis Vclosed by the'gyroscopic means upon inclination of the aircraft inany direction, and a pair of trim control means for each movable trimcontrol member and each controlled by a switch means to adjust theposition of at least one trim control member upon inclination of theaircraft; and manually operable trim control means connected with thecage means to independently adjust the position of the latter.

15. A gyroscopic trim control for rotary Wing aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomprising a movable trim control member adapted to be connected to afixed part of the aircraft and to the azimuth plate, cage means adaptedto be mounted upon the aircraft for inclination with respect thereto,gyroscopic means mounted upon the aircraft for universal inclinationwith respect thereto, means to drive the gyroscopicmeans, dampersVconnected with the -gyroscopic means which render the latterinsensitive to a short term change of attitude of the aircraft butchange its inclination upon long term change in attitude of the latter,a pair of switch means carried by the cage means and operated upon asmall movement of the cage means relatively to the Agyroscopic means toclose one of the switches of the pair, and means operated by eachswitch-means and connected with the movable trim control kmember toadjust the latter and hence the azimuth plate upon inclination of theaircraft.

16. A gyroscopic trim control for rotary Wing aircraft having auniversally inclinable Vazimuth plate for pitch control of the wingscomprising a movable trim control member adapted to be connected to afixed part of the aircraft and to the. azimuth plate, cage means adaptedto be mounted upon the aircraft for inclination with respect thereto,gyroscopic means mounted upon the aircraft for universal inclinationwith respect thereto, means to drive the gyroscopic means,`

dampers connected with the gyroscopic means such that the latter isinsensitive to a short term change of attitude of the aircraft butchange its inclination upon long term change in attitude of the latter,a pair of switch means carried by the cage means and operated upon asmall movement of Ythe cage means relatively to the gyroscopic means tovclose one of the switches of the pair,

meansoperated by each switch means and connected with the movable trimcontrol member to adjust the latter, the cage means and hence theazimuth plate upon inclination-of the aircraft, and manually operabletrim control means connected with the cage means to move the same.

17. A gyroscopic trim control for rotary wing aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomprising a movable trim control member adapted to be connected to axed part of the aircraft and to the azimuth plate, cage means adapted tobe mounted upon the aircraft for inclination with respect thereto,gyroscopic means mounted upon the aircraft for universal Yinclinationwith respect thereto, means to drive the gyroscopic means, dampersconnected with the gyroscopic means such that the latter is insensitiveto a short term change of attitude of the aircraft but change itsinclination upon long term change in attitude of the latter, a pair ofswitch means carried by the cage means and operated upon a smallmovement of the cage means relatively to the gyroscopic means to closeone of the switches of the pair, hydraulic valve means operated by eachswitch means, and hydraulic means connected with each pair of valves andthe movable trim control member to adjust the latter, the cage means andhence the azimuth plate upon inclination of the aircraft.

18. AV gyroscopic trim control for rotary wing aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomprising a movable trim control member adapted to be connected to afixed part of the aircraft and to the azimuth plate, cage means adaptedto be mounted upon the aircraft for inclination with respect thereto,gyroscopic means mounted upon the aircraft for universal inclinationwith respect thereto, means to drive the gyroscopic means,dampersfconnected with the gyroscopic means such that the latter isinsensitive to a Short term change of attitude of the aircraft butchanges n its inclination upon long term change in attitude of thelatter, a pair of switch means carried by the cage means and operatedupon a small movement of the cage means relatively to the gyroscopicmeans to close Aone of the switches of the pair, hydraulic valve meansoperated by each switch means, hydraulic means connected with valves andthe movable trim control member to adjust the latter, the cage means andhence the azimuth plate upon inclination of the aircraft, and manuallyoperable trim control means connected with the cage means to initiallymove the same.

19. A gyroscopic trim control for rotary wing aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomprising a pair of movable control members adapted to be connected toa fixed part of the aircraft and to the azimuth plate apart with respectto each other, cage means adapted to be mounted upon the aircraft forinclination with respect thereto, gyroscopic means mounted upon theaircraft'for universal inclination with respect thereto, means to drivethe gyroscopic means, dampers connected with vthe gyroscopic Ameans suchthat the latter is insensitive to ashort term change of attitude of theaircraft but changes its inclination upon long term change in attitudeof the latter, at least one pair of switch means carried by the cagemeans and operated upon a small movement of the cage means relatively-tothe gyroscopic means to close one of the switches of the pair, and meansoperated by each switch means and connected with the movable trimcontrol member to adjust the latter, the cage means and hence theazimuth plate upon inclination of the aircraft.

20. A gyroscopic trim control for rotary wing aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomprising a pair of movable trim control members adapted to beconnected to a fixed part of the aircraft and to the azimuth plate 90apart with respect to each other, cage means adapted to be mounted uponthe aircraft for inclination with respect thereto, gyroscopic meansmounted upon the aircraft for universal inclination with respectthereto, means to 'drive the gyroscopic means, dampers connected withthe gyroscopic means such that the latter is insensitive to a short termchange of attitude of the aircraft but changes its inclination upon longterm change in attitude of the latter,` at least one pair of switchmeanscarried by the cage means and operated upon a small movement of thecage means relatively to the gyroscopic means to close one of theswitches of the pair, means operated by each switch means and 'connectedwith the movable trim control member to adjust the latter and hence theazimuth plate upon inclination of the aircraft, and manually operabletrim control means connected with the cage means to move the same.

21. A gyroscopic trim control for rotary wing aircraft having aAuniversally inclinable azimuth plate for pitch control of the wingscomprising a pair of movable trim control members adapted. to beconnected to a fixed part of the aircraft and. to the azimuth plate 90apart Iwith respect to each other, cage means adapted to be mounted uponthe aircraft for inclination with respect thereto, gyroscopic meansmounted upon the aircraft for universal inclination with respectthereto, means to' drive the gyroscopic means, dampers connected withthe gyroscopic means such that 'the latter is insensitive to a shortterm change of attitude of the aircraft but changes its inclination uponlong term change in attitude of the latter, at least one pair of switchmeans carried by the cage means and operated upon a small movement ofthe cage means relatively to the gyroscopic means to close one of theswitches of the pair, hydraulic valve means operated by each switchmeans, and hydraulic means connected with each pair of valves and themovable trim control member te adjust the latter, the cage means andhence the azimuth plate upon inclination of the aircraft.

22. A gyroscopic trim control for rotary wing aircraft having auniversally inclinable azimuth plate for pitch control of the wingscomprising a pair of movable trim control members adapted to beconnected to a xed part of the aircraft and to the azimuth plate apartwith respect to each other, cage means adapted to be mounted upon theaircraft for inclination with respect thereto, gyroscopic means mountedupon the aircraft for universal inclination Iwith respect thereto, meansto drive the gyroscopic means, dampers connected with the gyroscopicmeans such that the latter is insensitive to a short term change ofattitude of the aircraft but changes its inclination upon long termchange in attitude of the latter, at least one pair of switch meanscarried by the cage means and operated upon a small movement of the cagemeans relatively to the gyroscopic means to close one of the switches ofthe pair, hydraulic valve means operated by each switch means, hydraulicmeans connected with each pair of valves and the movable trim controlmember to adjust the latter, the cage means and hence the azimuth plateupon inclination of the aircraft, and manually operable trim controlmeans connected with the cage means to move the same.

GLIDDEN S. DOMAN.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,921,805 Bordoni Aug. 8, 19332,023,105 Smith Dec. 3, 1935 2,368,698 Young Feb. 6, 1945 '2,384,516Young Sept. 11, 1945 2,389,798 Main Nov. 27, 1945 2,394,846 Cox s Feb.12, 1946

